The present invention relates generally to electro-optical displays, and more particularly, to drive circuits with available digital storage for generating modulated waveforms, driving display elements of a display device.
An array of display elements (e.g., pixels) in a display device may be driven using drive signals, such as modulated waveforms. In doing so, each modulated waveform may individually drive a different pixel of the display device. There are many ways to generate these drive signals.
One approach involves using pulse width modulation (PWM) which is a well-known technique, having a host of applications including in display systems. By generating pulse width modulated waveforms, pixels with digital storage, such as in liquid crystal displays (LCDs) may be driven. For instance, a spatial light modulator (SLM) uses an electric field to modulate the orientation of a liquid crystal (LC) material. By the selective modulation of the LC material, an electronic display of an image may be produced on a screen, as the orientation of the LC material affects the intensity of light going through the LC material. Sandwiching of the LC material between an electrode and a transparent top plate, for example, may enable the modulation of the optical properties of the LC material. When the voltage applied across the electrode and the transparent top plate is changed, the LC material may produce different levels of output intensity, altering the image produced on the screen.
However, allowing a duty cycle of a drive signal to vary as a non-linear function of a pixel value within a refresh period may result in multiple “ON” pulses. Several existing PWM-based schemes for driving pixels rely on adding up non-overlapping waveforms to build a PWM waveform, causing undesirable multiple edges in the PWM waveform. Generation of such multiple-edged PWM waveform may fail to appropriately control the LC material. Unfortunately, while displaying an image, this lack of drive control may result in an inadequate control over optical outputs from pixels being driven. That is, this technique may produce undesired, multiple, intermediate sub-levels of intensity while transitioning between different desired levels of intensity.
Thus, there is a need for better ways to controllably drive display elements in display systems with available digital storage.